Pulmonary circulation, edema, and pleural fluid Flashcards
What are the 3 circulatory systems in the lungs?
- pulmonary circulation. High flow, low pressure.
- the pulmonary artery has high compliance –> allows for stroke volume from the R ventricle with minimal increase in pressure - Bronchial circulation. High pressure, low flow
- 1-2% of total cardiac output
- oxygenated blood for all lung tissues
- empties directly into the pulmonary veins, so the L ventricular output > R ventricular output - Lymphatic circulation
- any particulate or leaked protein will be removed via the lymphatic system
How is the blood flow distributed in the lungs?
Pulmonary blood flow is almost equal to cardiac output
- pulmonary blood flow distribution is controlled by O2 level –> if low, there will be vasoconstriction, to shunt blood away from the poorly ventilated parts of the lungs
- there is minimal autonomic control of the pulmonary blood flow, BUT, sympathetic stimulation can lead to vasoconstriction, especially in the large pulmonary capacitative vessels – veins –> allows for displacement of extra blood in the lungs to other parts of the body to counteract hypotension
What are the 3 zone of pulmonary blood flow?
Zone 1: no blood flow. Alveolar pressure > arterial pressure > venous pressure
Zone 2: intermittent blood flow. During systole, the arterial pressure > alveolar pressure, but decreases during diastole (no blood flow)
Zone 3: continuous blood flow. Arterial pressure > alveolar pressure during all cardiac cycle. When a healthy person is lying down, all lungs are in zone 3
How does pulmonary resistance decrease during heavy exercise?
- increasing the number of open capillaries
- by distending the capillaries and increasing the flow through each capillaries
What are some important difference between pulmonary and peripheral circulation?
- pulmonary capillary pressure is low
- interstitial fluid pressure is also more negative
- capillary permeability is high – more leakage of protein –> high interstitial fluid osmotic pressure
- alveolar epithelium is very thin – easily ruptures if the interstitial fluid pressure goes about atmospheric pressure (0) – allows for fluid dumping into the alveoli
What’s significance of the +1mmHg mean filtration pressure?
This means that the slight higher filtration pressure will cause a continual loss of fluid from the pulmonary capillaries into the lymphatics
What are some causes of pulmonary edema?
- left sided heart failure/ mitral valve stenosis –> leads to a back up of blood into the lungs –>greatly increases the pulmonary capillary pressure –> flooding of the interstitial spaces and alveoli
- Damage to the alveolar epithelium (ex. noxious gas) –> leakage of fluids/ proteins into the interstitial space
What are 3 safety factors that prevents pulmonary edema?
- normal negative interstitial pressure: any slight increase in fluid will be “sucked” into the lung interstitium
- lymphatic drainage system: can proliferate and expand greatly given some time to help with excess drainage
- colloid osmotic pressure of the interstitial fluids will be decreased if there is an increased fluid loss during protein washout
What are the 4 main causes of pleural effusion?
- blockage of lymphatic drainage from the pleural cavity
- cardiac failure, leading to excessively high peripheral and pulmonary capillary pressure
- decrease plasma colloid pressure
- increased capillary permeability